A conductive paste containing silver particles has been used for forming electrode or a circuit pattern of an electronic part. Such a conductive paste has been used, for example, for a conductive circuit on a printed circuit board, an electrode of a capacitor, etc. As such a conductive paste, a conductive paste containing an amine salt of phosphoric acid with conductive metallic particles to improve preservation stability or dispersibility of the metallic particles in an organic solvent of the paste has been proposed (Patent Document 1).
In addition, as a conductive paste, a conductive paste containing metallic particles and a surfactant having a phosphoric acid group has been proposed to improve dispersibility of the metallic particles (Patent Documents 2 to 6). These conductive pastes are to suppress aggregation of the metallic particles in the conductive paste by attaching the phosphoric acid group contained in the surfactant to the metallic particles having high reductivity, and covering the surfaces of the metallic particles by the surfactant having the phosphoric acid group as a protective substance.
In recent years, in addition to polyimide flexible circuit boards, there is a movement to use an inexpensive PET (polyethylene terephthalate) film, PEN (polyethylene naphthalate) film, etc., as a substrate in the fields including mobile phones. In the field of using these substrates, a paste capable of being sintered at a low temperature of 300° C. or lower, more preferably 200° C. or lower is required. Under such circumstances, in recent years, a paste using silver fine particles which can be sintered at a relatively low temperature has been desired to be used in not only a conductive paste but also in a thermally conductive paste usable as a bonding member in a semiconductor device such as a bump and a die attachment member, etc.,.